[clang] Add -fkeep-system-includes modifier for -E (PR #67684)

[Paul T Robinson via cfe-commits]

pogo59 wrote:

Aha! Thank you. I should have found that third one in my searches, although it doesn't really describe the options that affect `-E` mode. The first link does, somewhat, and seems like the right place to add this new option. I'll have a go at that.

https://github.com/llvm/llvm-project/pull/67684